1. Field of the Invention
The present invention relates to a communication transceiver architecture and, more particularly, to a full-duplex free-space laser communication system.
2. Description of the Related Art
Free space laser communication systems offer the potential to transmit data at very high data rates over long distances. Due to the spatial coherence of laser sources, long range transmission is possible at modest power levels compared to RF systems. Further, the modulation frequencies of lasers allow for gigahertz bandwidths and are limited only by the current state of electro-optic components.
However, operating conditions such as atmospheric turbulence and cloud obscurations affect the performance of free space laser communication systems. Consequently, communication systems relying solely on laser signals at optical wavelengths may suffer periods in which communication is severely diminished or entirely precluded.
Moreover, adapting free space laser communication systems to moving platform environments such as airborne, space, and ground vehicles presents difficult technical challenges such as developing accurate angular pointing and tracking and achieving greater component ruggedness. Current laser communication systems are bulky, fragile, and not compatible with moving platform environments. Particularly with airborne platforms, where movement of aircraft can be unpredictable, it is critical that the pointing and tracking scheme provide accurate guidance for directing the data laser beams. However, lasers for pointing and tracking may be difficult to align to the data optical axis, and the transmitter and receiver configuration may be susceptible to even small misalignments. Also, many proposed systems employ laser wavelengths that are not eye-safe.
Further, typical free-space laser communication schemes are not suitable for developing a network-like communication capability among a number of moving platforms. For example, transmitters and receivers of proposed laser communication systems commonly employ static wavelengths and polarizations, thereby limiting the flexibility of such systems. Consequently, full-duplex operation is generally not possible with such schemes, particularly in a network context. Accordingly, practical free space laser communication systems have yet to be developed successfully for use in airborne and space environments.